A 20-year rise in cardiovascular disease (CVD) in China appears to have been spurred largely by increases in high blood pressure, according to a new study from Harvard TH Chan School of Public Health. Increasing body mass index (BMI), decreasing physical activity, a high prevalence of smoking, and unhealthy diet have also contributed to the growing burden of CVD, now the leading cause of death in China.
This is the first large study to analyse a wide range of dietary, lifestyle, and metabolic risk factors that may be impacting CVD burden in China. The authors suggested that major changes in Chinese society, including a dramatic shift from a traditional to a more ''Western'' diet and lifestyle and rapid urbanisation and industrialisation might have contributed to the jump in cardiovascular diseases, such as heart attack and stroke. These changes have been accompanied by marked increases in high cholesterol, obesity, and type 2 diabetes among the Chinese population.
''We described trends from 1991 to 2011 in dietary and other lifestyle risk factors for CVD in China and projected how these trends might play out from 2011 to 2031,'' says Yanping Li, research scientist in the Department of Nutrition at Harvard Chan School and lead author of the study. ''Our estimates suggest that the continued rise in high blood pressure, an increasingly sedentary lifestyle, increasing obesity, and worsening dietary trends will add millions of new cases of heart attacks and stroke over the next two decades.''
The researchers analysed data collected over a 20-year period, from 1991-2011, from 26,000 people living in nine Chinese provinces, as part of the China Health and Nutrition Survey.
They looked at 17 dietary and lifestyle risk factors that had been previously linked with heart attack and stroke, including high systolic blood pressure, high cholesterol, high blood glucose, high BMI, low physical activity, smoking, and 11 dietary factors and analysed that data along with information on CVD-related disease and death incidence extracted from the China Health Statistical Yearbook and the National Population Census.
The study found that high blood pressure, high cholesterol, and high blood glucose accounted for most of the CVD disease burden in China in 2011. That year, those three risk factors were associated, respectively, with 3.1, 1.4, and 0.9 million new cases of heart attack or stroke. Of 6.8 million Chinese over age 35 who died in 2011, about 3 million of the deaths, 44 per cent were CVD-related.
The researchers estimated that high blood pressure alone was responsible for roughly 40 per cent of heart attacks or stroke. High blood pressure had jumped dramatically in China over the past three decades, the authors noted: In 1979, its prevalence in the population was 7.7 per cent; by 2010 it was 33.5 per cent comparable to that among US adults.
The study also found that decreased physical activity during the study period was associated with a 0.7 million increase in CVD cases and BMI increases were associated with a 0.6 million increase.
Although tobacco use is declining in China, a large percentage of the population still smokes (53.4 per cent of men); the study found that, in 2011, tobacco use was associated with 1.3 million CVD-related cases, roughly a third of the CVD burden in men.
The authors also noted that while the Chinese diet had improved in certain ways, with increased consumption of fibre, fruit, nuts, and omega-3 fatty acids-dietary quality was still far short of optimal goals. Consumption of red meat and sugary beverages was increasing and high sodium intake, which averaged 5.4g/day in 2011was estimated to be responsible for one fifth of CVD cases in China.
Both increases in high blood pressure and increases in BMI over time were more pronounced among younger people and rural residents, the authors said.
''China is facing a rising epidemic of cardiovascular disease and it shows no sign of abating,'' said senior author Frank Hu, professor of nutrition and epidemiology at Harvard Chan School. ''It's imperative to continue to monitor the problem, which has serious social and economic consequences. Prevention of chronic diseases through promoting healthy diet and lifestyle should be elevated to a national public policy priority.''
Other Harvard Chan School researchers involved in the study included Dong Wang, Sylvia Ley, Yuan Lu, and Goodarz Danaei.
Funding for the study came from the Swiss Re Foundation.